This invention relates generally to calibrating electronic devices, and more particularly, to calibrating radio-frequency circuitry in wireless communications devices.
Electronic devices such as handheld electronic devices and other portable electronic devices are becoming increasingly popular. Examples of handheld devices include handheld computers, cellular telephones, media players, and hybrid devices that include the functionality of multiple devices of this type. Popular portable electronic devices that are somewhat larger than traditional handheld electronic devices include laptop computers and tablet computers.
Electronic devices such as portable electronic devices are often provided with wireless communications capabilities. For example, handheld electronic devices may use long-range wireless communications to communicate with wireless base stations and may use short-range communications to communicate with accessories and local networks.
Electronic devices with wireless communications capabilities often undergo calibration operations during manufacturing. A typical device includes a processor and other circuitry that generates data. A typical device also includes radio-frequency transceiver circuitry for transmitting and receiving data over an antenna. Amplifiers may be used to increase the strength of the radio-frequency signals. For example, adjustable-gain radio-frequency power amplifier circuitry may be used to amplify transmitted radio-frequency signals. If the power amplifier circuitry is not properly calibrated, the device may produce radio-frequency signals that are too weak or too strong. Signals that are too weak may cause the device to operate incorrectly. Signals that are too strong may lead to operational and regulatory compliance problems.
Conventional calibration systems are built around complex and expensive radio communication test equipment. In a typical scenario, a device to be calibrated is placed in a shielded box and connected to a radio communication tester and a computer via cables. During calibration operations, the radio communication tester establishes a bidirectional communications link with the device and characterizing radio-frequency signal measurements are made. The results of these measurements are then processed to produce power measurement data for device calibration.
With conventional calibration schemes of this type, the process of establishing the wireless communications link between the tester and the device limits production line throughput. Moreover, the radio communication test equipment uses expensive spectrum analyzing circuits in making signal measurements, which adds to the complexity and cost associated with calibration.
It would therefore be desirable to provide improved techniques for calibrating radio-frequency circuitry in wireless communications devices.